From 67bf966a6a2e14cebb1593d67d565c4bcbc12dee Mon Sep 17 00:00:00 2001
From: Arthur Lu <learthurgo@gmail.com>
Date: Fri, 14 Feb 2025 22:35:54 +0000
Subject: [PATCH] add tiered cache
---
tiered_cache.py | 94 +++++++++++++++++++++++++++++++++++++++++
tiered_cache/.gitignore | 2 +
2 files changed, 96 insertions(+)
create mode 100644 tiered_cache.py
create mode 100644 tiered_cache/.gitignore
diff --git a/tiered_cache.py b/tiered_cache.py
new file mode 100644
index 0000000..3954b20
--- /dev/null
+++ b/tiered_cache.py
@@ -0,0 +1,94 @@
+from cache import BaselineCache
+from collections import OrderedDict
+import os
+
+class TieredCache(BaselineCache):
+ l2_limit = None
+ l2_map = None
+
+ def __init__(self, limit, l2_limit = 100):
+ super().__init__(limit)
+ self.l2_limit = l2_limit
+ self.l2_map = OrderedDict()
+
+ def get(self, key):
+ # first look in the l1 cache
+ s = super().get(key)
+ if s != None:
+ return s
+ else: # on a miss, check the l2 cache mapping
+ if key in self.l2_map: # if it is in l2 cache (disk), open the file and return the values
+ f = open(self.l2_map[key], "r")
+ v = f.read()
+ f.close()
+ return v
+ else: # otherwise its a cache miss and return None
+ return None
+
+ def put(self, key, val):
+ evict = False
+ if len(self.cache) >= self.limit:
+ if len(self.l2_map) >= self.l2_limit:
+ self.l2_map.popitem(last = False)
+ evict = True
+
+ k,v = self.cache.popitem(last = False)
+ path = f"tiered_cache/{k}"
+ self.l2_map[k] = path
+ f = open(path, "w+")
+ f.write(v)
+ f.close()
+
+ self.cache[key] = val
+
+ return evict
+
+ def invalidate(self, key: str) -> bool:
+ # basic delete invalidation, no (p)refetching
+ if key in self.cache:
+ del self.cache[key]
+ return True
+ elif key in self.l2_map:
+ os.remove(self.l2_map[key]) # this is so sketchy
+ del self.l2_map[key]
+ return True
+ else:
+ return False
+
+if __name__ == "__main__": # basic testing, should never be called when importing
+ cache = TieredCache(10)
+
+ for i in range(10):
+ assert cache.put(str(i), str(i+1)) == False
+
+ assert len(cache) == 10
+ assert cache == OrderedDict({'0': '1', '1': '2', '2': '3', '3': '4', '4': '5', '5': '6', '6': '7', '7': '8', '8': '9', '9': '10'})
+
+ assert cache.get("5") == "6"
+ assert cache.get("8") == "9"
+ assert cache.get("0") == "1"
+
+ assert len(cache) == 10
+ assert cache == OrderedDict({'1': '2', '2': '3', '3': '4', '4': '5', '6': '7', '7': '8', '9': '10', '5': '6', '8': '9', '0': '1'})
+
+ assert cache.get("a") == None
+ assert cache.get("b") == None
+ assert cache.get("c") == None
+
+ assert cache.put("a", "b") == False
+ assert cache.put("b", "c") == False
+ assert cache.put("c", "d") == False
+
+ assert len(cache) == 10
+ assert cache == OrderedDict({'4': '5', '6': '7', '7': '8', '9': '10', '5': '6', '8': '9', '0': '1', 'a': 'b', 'b' : 'c', 'c': 'd'})
+
+ assert cache.get("c") == "d"
+ assert cache.get("b") == "c"
+ assert cache.get("a") == "b"
+
+ assert cache.get("1") == "2"
+ assert cache.get("2") == "3"
+ assert cache.get("3") == "4"
+
+ assert len(cache) == 10
+ assert cache == OrderedDict({'4': '5', '6': '7', '7': '8', '9': '10', '5': '6', '8': '9', '0': '1', 'c': 'd', 'b' : 'c', 'a': 'b'})
\ No newline at end of file
diff --git a/tiered_cache/.gitignore b/tiered_cache/.gitignore
new file mode 100644
index 0000000..c96a04f
--- /dev/null
+++ b/tiered_cache/.gitignore
@@ -0,0 +1,2 @@
+*
+!.gitignore
\ No newline at end of file